Most adults over the age of 65 and a growing number in mid-life are living with two or more chronic medical conditions (multimorbidity), and multimorbidity is strongly associated with risk of subsequent disability and mortality. Increasing attention is being devoted to identifying those adults who are most vulnerable to adverse outcomes and to treating their multiple conditions effectively, and by far the bulk of this researc centers on factors that increase the risk of multimorbidity burden and the likelihood that multimorbidity will result in functional declines. The proposed research is designed to address two significant gaps in the multimorbidity literature. The first is the potential role of psychosocal resources in preventing or delaying multimorbidity in aging adults and in protecting against functional declines and greater mortality that are typically associated with multimorbidity. The second is a biopsychosocial perspective that recognizes that multimorbidity and its consequences are likely to involve complex interactions of social, psychological, and biological processes. We focus on two psychosocial resources - a strong sense of purpose in life and positive social relationships - that we and others have linked to better health outcomes and reduced mortality in clinical sample and large epidemiological studies. We propose to examine the contribution of psychosocial resources to (a) reduced and/or delayed development of multimorbidity burden and (b) reduced or delayed declines in functional and cognitive abilities and in mortality in adults with multimorbidity. We will also examine the extent to which psychosocial resources are linked to reductions in multimorbidity, functional declines, and mortality in aging adults at greater risk of all of these outcomes due to sociodemographic risk factors (e.g. age, female gender, low educational attainment). Finally, consistent with our integrative perspective, we will examine the role of a well-defined biological process - inflammation - as a potential mediator of (a) the links between multimorbidity and functional and mortality outcomes and (b) psychosocial moderation of the links between multimorbidity and these outcomes. That is, we hypothesize that psychosocial resources will act through reduced circulating levels of inflammatory proteins to weaken the link between multimorbidity and adverse outcomes, thereby enabling aging adults to live well with multimorbidity. We will test these hypotheses using data from three waves of the Survey of Mid-Life in the United States (MIDUS). MIDUS is the ideal forum for our analyses, as it brings together high quality assessments of health, psychosocial functioning, and biological processes related to health in a large population-based study. The longitudinal structure of MIDUS will enable us to examine change over time in predictors, outcomes, and their associations, and our analytical approach will use multilevel models and moderated mediation analyses to provide precise tests of our key hypotheses. Finally, as the psychosocial resources that lie at the heart of the application are modifiable, the results of this study will point directly to novel ways to improve health and well-being in adults with multimorbidity.